Shortly after 12 p.m.: The attack began at Nairobi's Westgate Mall with bursts of gunfire and grenades.
• The shooting began downstairs and outside, then the gunmen came inside.
• At least five gunmen — including at least one woman — first attacked an outdoor cafe at the mall.
• Eight gunmen with scarves twisted over their faces fired at shoppers and then up at Kenyan police officers who were shooting down from a balcony as panicked shoppers dashed for cover.
• The gunmen entered the mall through the front entrance and through parking. Lights went out.
• Shoppers — expatriates and affluent Kenyans — fled in any direction that might be safe: into back corners of stores, back service hallways and bank vaults.
•Two squads of gunmen moved through the mall.
• The gunmen let Muslims go.
• Thirty Americans citizens, including U.S. embassy personnel, were in the mall at the time of the attack, according to a U.S. official. All were evacuated and are accounted for, the official said.
• A festival with more than 50 children attending was occurring at the time of the attack.

Over the next several hours: Pockets of people trickled out of the mall as undercover police moved in. Some of the wounded were trundled out in shopping carts.
• Bloodied victims were being loaded onto ambulances, and a local hospital was overwhelmed with the number of wounded being brought in and diverted them to a second facility.
• Kenyans turned out in droves to donate blood, officials said.

Mid-afternoon: The U.S. embassy in Nairobi and the UK Foreign Office advised people to avoid public places, stay home and monitor local media.

4:44 p.m.: Kenya's interior ministry said the attack may have been carried out by terrorists. (BBC)

Late afternoon: A series of tweets from Twitter accounts reportedly associated with al-Shabaab claimed responsibility for the attack, although ABC News has not verified the accounts' authenticity.

As night fell: Two contingents of army special forces troops moved inside the mall. Police and military surrounded the huge shopping complex as helicopters buzzed overhead. (AP)

Around 10:15 p.m.: Kenyan President Uhuru Kenyatta said in a televised address that some of his family members were killed in the attack. The attacks sought to intimidate and divide the nation, he added, but "we have overcome terrorist attacks before. We will defeat them again."

11:00 p.m.: The Elysee Palace said in a statement that two French citizens were among the victims.

11:30 p.m.: National Security Council spokeswoman Caitlin Hayden said in a statement that the "United States condemns in the strongest terms the despicable terrorist attack on innocent civilians today."

SEPTEMBER 22

Overnight: The military pushed back the perimeter around the Westgate.

Around 2 a.m.: Canadian Prime Minister Stephen Harper said in a statement that two Canadians, including one diplomat, were among those killed in the attack.

Around 2:15 a.m.: Secretary of State John Kerry released a statement saying that several American citizens had been injured, but that there were no reports of any killed. The wife of a foreign service national working for the U.S. Agency for International Development had died, though, he said.

3:47 a.m.: The UN Security Council released a statement that its members "condemn in the strongest possible terms today's terrorist attack in Nairobi."

Around 9:30 a.m.: A barrage of gunfire erupted from the mall, and moments later two wounded Kenyan security forces were carried out of the building.

11 a.m.: Security remained tight around the Westgate, with helicopters hovering overhead.

Around 11:55 a.m.: Kenyan Interior Cabinet Secretary Ole Lenku said at a press conference that 59 people had been confirmed dead and at least 175 people had been injured. Ten to 15 attackers were still in the mall, and 1,000 people had been rescued so far, he said. Kenyan security forces were in control of the CCTV room and were monitoring the situation, he added. There were still some people inside the mall, and the situation remained a national security operation, he added.
• Note: A full 24 hours passed since the attack began.

6:20 p.m.: Police have pushed back the perimeter and blocked more roads.

The Associated Press, the New York Times and the BBC contributed to this report.